Methods and means for utilizing a direct-view type electrical storage tube



H. O. HOOK S' FOR July 15, 1958 v y 2,843,798 K METHODS AND MEAN UTILIZING A DIRECTQVIEW TYPE ELECTRICAL STORAGE TUBE Filed May 29,l 1955 fhl Zl'/ F' .1. WMM@ aa/v a NZ R. o.. m mm m n. f .Wl/n. M/ in I H d WW1- m 4 U p/wn wij 0./ Y 0M d l E y 0 l., 0 V #1, M 'ww m .rv/ 5 i WVM UH.. MM I. W W... n/Lw zi. Z i Zz zu... n am .MW we Jr i if ..o awumm- ...M/mmm Wm ...2.... lfm y. MM A@ mm m i I M 1:... www uw@ 6. w T 4 n m l.. #w ls... w. F s H W/a.

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TTORNEY United States ParentA METHODS ANDr MEANS FOR UTILIZINC A DIRECT-VIEW TYPE ELECTRICAL STOR- AGE TUBE Harvey 0. Hook, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application May 29, 1953, Serial No. 358,361

' 1o claims. (c1. 315-12) This application is a continuation-impart of my original application Serial No. 306,709', led August 27, 1952,

assigned to the same assignee as the instant application and which is now abandoned.

This invention relates lgenerally to signal lstorage and displayrsuch systems usually require a 'pictorial display tube and also one or more electrical storage tubes.

' Since at least. two cathode ray devices are required, it

will be seen. that the circuitry for use therewith (i. e., deilection generators,,synchronizers, deflection. yokesl and/ or sweep resolvers, amplifiers, etc.) is extensive. This is prohibitive not only economically` and practically but yalso spatially (particularly in airborne systems). Itis desirable to employ a system utilizing a single cathode ray devicein which. there is provided the features of both signal storage and display. l

b Such a tube has been developed and is described in detailI in now abandoned patent application, Serial No. 254,999, tiled November 6, 1951, by Max Knoll. and in a. continuation-impart thereof Serial No. 295,768, tiled .lune 26, 1952, by the same inventor. In addition to the combined storager and. display features mentioned above, other advantages. of the direct-view storage tube include greater picture brightness for a given anode voltage, less iiicker for a. given signal bandwidth, a picture storage time of several minutes substantially Vwithout picture decay, and less extensive associated system circuitry.

In the aforementioned' Knolly patent. applications, data displayed by the direct-view tube is'V completely and instaneously, erased by manually adjusting the amplitude andpol'arity of potentials which are applied to certain' electrodes contained therein. According to the present. inventionthese potentials periodically and recurrently are controlled in a predetermined manner to achieve a desired result'. For example, in one modevof operation information stored and displayed in the abovetube in-V cre'mentall-y maybe erasedduring the interval following tliewr'it'ing of'. each line of data. ,Affractional/ portion of the overally stored electrical charge pattern is erased in the time interval'bet'ween` the end ofthe Writing of one line of data and the beginningof the writing ofthe next succeeding line of data. By controlling .the Vextent of incremental erasure d'uri'ng, each` such interval, it will be seen that' a given line of oldy data may be completely erased' substantially immediately before being, replacedj with,

new data. l Y

Signall integration and noise discrimination also may be* achieved, according' to aY further feature' of thel mventibil byniodifying'ftlie erasing systenrV operation to eras'ef data incrementally' during: tlieintervalsbetween the writ@ ing of successive frames of during a given erase period, the desired signals arelfr'e-f written in each succeeding' frame and are.irtleg'rgited,v The noise'signals, however, arel statistical in nature audec'eur randomly. Thus over several frame times the undesired noiseA signals 'are almost completely' eliminated. b ln the line-by-line and frame-by-frame'erasingand iti?2 tegrating arrangements mentioned above pulses' are aip-L plied to the tube to control erasure. Accordinglto another feature of the invention llong time storage fof e'lectridall data is afforded,y Without: erasure, .by 'writingl a frame'of data during predetermined writingl intervals' and l'nya'pd plying pulses tothe tube, betweensuccessive*writingl inter`a` vals,fwhich have amplitudesgreater thanthepulse ampli# tuderrequired for" erasure. By this means electrical charge data storedvon a storage insulator is maintained. for an' extremely longp'erio'd ottimeV y v- Y 1*".

A11 object of the invention' is toy provide improved methods-of and meansffor storing electrical data.

An object of theinstant invention is` tov provide an improved land ,simplified signal display system.

Another object of the invention is to provide a signal display system which: is tiexible in ,itsdield' of application.; Another object of. the invention is to' provide improved methods and meansH for utilizing the direct-viewstorage tube. Y l

l A further object of the-invention is toj provide improved methods and means for erasing in the direct-view storage tube.

A stillfurtherv objectv of: the invention Visto provide an improved signal display system providing signal integration and noise discrimination. e f i' A still further `objectv of lthe invention is to provide an improvjed signal storage and. display system providing longtime storage of electrical data. lThe invention will be described in detail with reference t'o the accompanying drawing in which: n i

Figure 1 isa cross-sectional schematic diagram,` partially in block form, of a .directview storagetube and an erasing system therefor, according to the /inventiongfand Figure 2 is a schematic diagram, inV block form, of. amodification of the erasing system shown in Figurefl.I Similar reference characters are applied. tol similar ele:y ments throughoutthe drawings...

data stored andf displayed Storage tub'e structure b Figure 1 ofthe drawing' shows adireetvie'w type storage tube consisting of ajn` evacuated envelope, 10` having two neck sections 12 and" 14, respectively.` ,Within the envelope neck 12 is" an electron' gun 16, hereinafter referred to as the ,*vie'wi'ng gun. Within neck 14 is a second orw`riting electron gun 18 for. providing a modulated beamof'electrons which is accelerated into the envelope portion 10. I Mounted at the large end of thedenvel'ope portion 1'0 is an assembly 20 including a glass support sheet'22 having a thinconductive film 24 disposed on one, surface thereof andfacin'g the electron guns. .The 214 may bev formed, for eXample,fof a metal' or-rnetallic Acompound such as tin oxide- "On topi ofthe conductive .film 2`4is a layer 2,6formed from a yphosphor. materiallwhiehliuoresces underV electron bombardmen In the direction towards the ,electron guns assembly' 2'7 including a tine m'e'sh metal` screen layer Z6. A storage screen 30" is formed, byjevaporationy or some other convenient meansjon the surface ofltlie conductive* screen 281a'nd comprises a dielectric' insulatiing material suchas atiilnrof silica' or magnesium fluoride of' the order ofseveralE microns ine thickness. t adislV y information; Whietotu desired and "undesired signals (noise) are partiallyl erased from the. surface of the fluorescent layer 26, is` a. storage targetA l 2'8 spacedl at a distance of severalmillime'tersl from the fluorescent tance of the order of `ten millimeters from the conductive l screen 28 in the direction towards the electron guns is a second ne mesh metal screen 32. Screen 32 may be a woven stainless steel screen of the order of 230 lines p er inch while the conductive screen 28 and the storage screen 30 may have a neness ofY the, order of 200 lines per inch.

Assembly 20 is mounted on a ring 36 of insulating material fixed within the envelope 20 and adjacent the tube face plate 38. Fixed to the ring 36 is an annular metal support ring 40 which supports intermediate its ends the glass support sheet 22 and across its open end the conductive screen 28. Also mounted on the insulating ring 36 is a second annular metal support ring 42 across the ends of which is mounted the woven metal mesh screen 32. The conductive tin oxide iilm 24 is insulatedfrom the support ring 42 by the glass sheet 22 and is connected by a lead 44 to a source of positive potential outside the envelope 10. Mesh screen 32 also is connected to a source of positive potential via lead 46. The conductive screen 28 during the tube operation, is set either at ground potential for writing or at a more positivepotential of the order of twenty volts for erasure, as will be shown hereinafter.

The viewing gun 16 comprises a cathode electrode 48, a control electrode 50, a first accelerating electrode 52, and a second accelerating electrode 54 mounted successively along the axis of the gun 16 toward the face plate 38. During the tube operation these electrodes are maintained at appropriate voltages to form the electron emission from the cathode 48 into a wide beam or spray 56 of electrons. The inner surface of the envelope has applied thereto a conductive coating 58 of colloidal graphite which coating may be maintained at the same positive potential as the second accelerating electrode 54. A second wall coating 60 extends from a point spaced from but adjacent coating 58 over the bulb wall enclosing the assemblies 20 and 27. This coating is at a potential dilferent from that of coating 58 and thus provides a collimating electron lens to align the electrons of the spray beam 58 in a direction axially with respect to the target assemblies.

The writing electron gun 18 comprises a cathode electrode 62, a control electrode 64 and, successively spaced toward the target, a first accelerating electrode 66 and a second accelerating electrode 68. The Wall coating 58 extends into the neck 14 of the Writing gun and forms a third accelerating electrode for forming the electrons of gun 18 into a sharply defined and focussed beam 70.

The voltages applied to the electrodes of the above tube are illustrative of typical suitable operating voltages but should not be considered as limiting.r For example, the mesh screen 32 may be operated at between 200 and 2,000 volts positive with respect to ground. The conductive coating 24 may be operated within a range of from 2,000 to 20,000 volts positive relative to ground, while the potential applied tothe conductive screen 28 may be varied from minus 100 volts to positive 2,000 volts relative to ground.

Tube operation To prepare the storage target for storing a charge pattern on the mesh storage screen 30, it is necessary to establish a uniform potential thereover. With the viewing gun turned on, the electrons of the spray beam 56 are accelerated with energies up to 1,000 volts through the metal mesh screen 32. The potential of conductive screen 28 is set to a potential suicently positive (of the order of 20 volts positive relative to ground) that the electrons of the spray beam 56 strike the surface of the storage screen lilm 30 at velocities or energies to initiate secondary emission from all portions of the iilm. In the present example the positive potential of 20 volts which is applied, as described hereinafter, to the conductive screen 30 is below rthe first cross-over point on the secondary ratio curve of the silica (or magnesium fluoride) lm. The iirst crossover point for a silica storage lm is of the order of 75 to 150 volts while the first crossover point for a magnesium iiuoride film is approximately 30 to 60 volts. Thus secondary emission is initiated having a ratio less than unity and the storage screen 32 assumes a uniform potential, in this instance viewing gun cathode potential. The entire surface of the storage screen may be completely erased to a uniform potential as described above in a fraction of a second.

The potential applied to the conductive screen 28 is then set to approximately ground potential. Because of the thinness of the storage screen 30, screen 30 is closely coupled capacitively to the screen 28, hence the relative potential difference therebetween is maintained; i. e., as the potential of screen 28 is changed from a 20 volts positive relative to ground to ground potential, the potential of screen 30 changes by a corresponding amount from viewing gun cathode potential (ground potential) to approximatley minus 2O volts relative to ground. The electrons of the spray beam 56 are accelerated through the mesh screen 32 and enter a retarding eld adjacent the screen 30, the retarding field turning the electrons back to the metal screen 32 which serves as a collector therefor. The 8,000 volt potential applied to the tin oxide lm 24 creates a field which tends to extend through the interstices of the storage screen 30 to draw electrons through the screen to bombard the uorescent layer 26. The voltage to which the storage screen 30 is set (minus 20 volts), however, just prevents any electrons from passing therethrough.

The writing gun 18 is then turned on and produces a sharply deiined and focused beam 70 which may be deected to scan over the surface of the storage insulator 30. The deflection may be accomplished, for example, by supplying vertical and horizontal pairs of deection plates 72 and 74, respectively, with suitable deilection signals from deflection generators 76 and 78, respectively. While the writing beam 70 is being deected in the desired pattern, the beam 70 is modulated by video signals appliedl to the writing gun control grid 64 from an input circuit 80. The writing beam impinges on the mesh storage screen 30 at a voltage of approximately 3,000 volts which is between the rst and second crossover points on the secondary emission ratio curve thereof.

In this manner the Writing beam initiates secondary emission from the surface of the storage screen such that more electrons leave the surface than impinge thereon. In those areas where the beam 70 strikes, the storage screen surface is driven positively from its potential of minus 20 volts toward viewing gun cathode potential or ground. Provided the ratio of the spray beam average current density to the average current density of the Writing beam over a given time interval is unity or greater, no point on the insulator surface will stay positively charged with respect to ground since electrons from the spray beam 56 land continuously at that point and drive it back to ground potential, or slightly negative with respect to ground. In the areas where the storage screen 30 has been driven positively (from minus 20 volts) the positive eld of the iiuorescent screen 26 now penetrates to draw the low energy electrons of the spray beam S6 through the interstices of screens 30 and 28 to strike the iiuorescent layer 26 and cause luminescence. This luminescence appears only on areas of the fluorescent layer 26 corresponding to areas of the storage insulator driven positively by secondary emission and hence corresponding to the image pattern of the writing beam.

This type of writing provides a visualV display in which stored information appears as White on a dark background. Once a signal has been stored and displayed, theoretically it should remain stored and displayed in- -a line of new data.

Erasing y Figure 1 shows an. erasing system, according to. one feature of the invention, for use with the direct-view storage tube Awhich system is adapted for cyclically and incrementally erasing data stored" and displayed thereby. A.. synchronizer 82 repetitively produces pulsesfat. a predetermined pulse repetition rate which pulses simultaneously are coupled to a horizontal deflection wave generator 78' and to ak pulse rate divider circuit 84. The divider circuit produces one output pulse'vr in, response to' a' predetermined number of input pulses-.` Assuming that the erasing is to be utilized in connection with la typical B-scan radar system, the divider circuit 84 may producey one output pulsey in response to each 6,000 pulses input thereto. This assumes a` synchronizer pulse repetition rate of 1,000 cycles per second and' an. azimuth scanningrate of one 360 search every six seconds. Each output pulse derived`v from the divider 84 is applied to a verticalv deflection wave generator 76. The horizontal and' vertical deflection generators 78: and 76, respectively, produce sawtooth. deflection signals whichi areapplied tothe pairs of deflection plates 72 andl74 ofl the storage. tube' to deflect the writing beamI '7,0' to rectil'inearly scan the storage screen 30.

During the horizontal dellectionintervals, video. sig.- nalsare applied to the writing gun control electrode 64 via input circuit 80@ and modulate .the intensity of the. writing beam 70- to establish a predetermined charge pattern on the storage screen'r 30 and a. corresponding visualydispl'ay on the fluorescent'layer 26. l

Simultaneous with the application of synchronizer pulses to the divider circuit 84 and to the horizontal. de.- flection generator 78,. the synchronizer pulses also arev successively applied to a time delay circuit 86 and. to

a one-shot multivibrator 88. The time delay provided. by thecircuit 86 is adjusted such that the leading edges. ofthe one-shot multivibrator pulses each occur slightly after v the writing of each line of information. The, multivibrator pulses thus producedare applied Ato an amplifier 91), preferably a cathode-follower, output sig,- nals. of which are developed across a load impedance 92 t'o periodically and instantaneously drive the conductive.

lscreen 2 8 of the storage tube approximately 20 volts' positively with respect to ground potential'. to. effect partial erasure ofthe stored data. Byv this means information stored in the direct-view tube incrementally is erased' in the flyback intervalffollowingv each writing.

interval. o

The erase interval. may be controlled by controlling the multivibrator pulse duration and the extent or depth of erasure may be' controlled by suitable adjustment of the amplitude ofthe erasingpulse. The erasingI pulse duration may be controlled, for example, by varying circuit constants in. the charging. circuit of the one-shot multivibrator 88 while. theA erasing. pulse amplitude may be: controlled` by means4 of a gain control circuit 94 associated with the amplifier 90.4 By properly adjusting the' amplitude. and. duration ofthe erasing pulse,- it willvbe seen that a given line of. data is partially erased during. each' flyback. interval. and is'` completely erased in one frame time and just prior to being replaced with Thus an up-to-date display of information is provided wherein old data cyclically may be erased and replaced with new information.

Signal integration and noise discrimination are afforded according to a further feature of the invention. According to this feature of the invention and referring to Figure 2 of' thel drawing, signals` applied?y to' theinput of the time d'elay circuit .86 are derived'y from.v the output circuit, rather than the input circuit, of'the'pulse rate divider'circuit 84. Thus erasing'pulsesv are produced only in thev time intervals between the writing: of'fsuc# cessive frames of information;

In this mode of operation, it will be seen-that both desired signals and noise signals are written during a given frame time and are partially erased -just' prior to the writing of the next frame of data. IIn the` next frame time the desired (and partially"verased)'" signals are rewritten to enhance the chargev pattern established during the writing of the precedingframe; The noise sig; Y

nals, however, because of their random"oc'currerrce are not rewritten in the same areas onthej tube storage screen 30 in successive frames'. Thus the desired'signal's are integrated and noise signals are erased. o Snce'thc normal tendency of the human eye is tdi'ntegrate the displayed information and since the lastk few' lines" of data written in a given frame are viewed for aA relatively short time compared to other lines of' data" previously written, it may bedesirable to' employ' a shading circuit such as avariable gain amplifier (not shown) to" bring up the level ofy data last written so that"'the overall' display appears to be of constant brightness.

The above erasing system' has been' described in connection Withthe writing, erasing, and displaying of; a

recti-linear B-scanv type radar presentation;v Itjisipointed" out, however, that the pulsing techniquesjlrerein pro? posedare of general applicability'. Television displays;` PP-Ij (plan-position indication), and other suchdf plays may be incrementally erased with'. equal facll'ity;

Longtime'. signal storage n v The :circuitry described. with reference. to Figure. l: may be used to achieve. long. timeL storage of' electrical. data rather thanincremental erasure. as heretofore-shown.; According to` this mode of Voperation the .gaincon-trol.

94 is set to control the gain of: the pulse arnplifierl90 sothat. the pulses `applied to the. conductive screen- '28 have. amplitudes of the order -of A volts fora/.magnesium fluoride insulator and amplitudes ofthe order of 100 volts. for a silica insulator, ineach. caser abovethe first crossover point. l y

.Under such conditions, for` the dura-tionsr` oftthcse pulses,v portions of they storage. insulaton 30k which: are. carried above first crossover potentiall are charged in a. positive, direction and portions vof the insulator below` the rst crossover point are charged. inn a` negative direc,v tion. The portions carried above the first lcrossover potential Icorrespond to highlight .portions ofthe' display provided on the fluorescent rlayer 26. whilethe insulator portions below lirst crossover correspond to' dark areas of.

.y the. display. A single frameof data stored in themanner described. above may be retained for aperiod of. time.

approximately 103 times longerjtnan` without pulsing.`

`In this mode of operation-thevpulses-produced-by.the

multivibrator 88l have durations short. enough so thatnof areaV of the storage insulator 30 remainsgequal toa-or Igreater than the first crossover voltage in' the, intervals between pulses. If the pulse. duration is toofgreag elec.-Y trons from the viewingy beamv 56 drive these' storage areas to the potential of. the collector screenv 321.. Then the: insulator 30 either may break down or the sizevof'storedi charge may increase` or diminish thereby elfectively creeping across the.V insulator.

What is claimedis: 1 1-. A signal storage systemyincluding, .an.electrical1 storage tube having an electron permeable charge storage member, means spaced from one side `of said charge storage member for providing a stream of electrons for ooding a major portion of the-surface of said member, a Illuorescent viewing screen yspaced from the opposite side of said Acharge storage member, means for providing a sharply defined and focused beam of electrons, means for delecting said sharplyv dened and focused electron beam acrossV said storage member, connection means for a source of Isignals for modulating said beam during said deflection to write an electrical charge patternv on said member, the charge pattern written on said member modulating the ow of said stream of electrons so that electrons' passing `through said electron permeable member impin-ge on said viewing screen and produce a Visual display corresponding to said charge pattern, and means coupledto said 'storage tube for repetitively generating pulses at a predetermined pulse repetition rate for periodically pulsing said charge storage member with respect to said flood beam generating means.

2. A system as claimed in claim 1, wherein said pulse generating means includes means for controlling the pulse duration of pulses produced thereby.

3.A system as claimed in claim 1, wherein said pulse generating means includes means for controlling the pulse amplitude of pulses produced thereby.

4. A system as claimed in claim 1, wherein said pulse generating means includes means for controlling the amplitude and duration of pulses produced thereby.

5. A system as claimed in claim 1, wherein said pulse generating means produces time spaced pulses which are yequal in amplitude.

6. A signal `storage system including, an electrical storage tube having a charge storage member, a iuorescent screen spaced from one side of said charge storage member, means for generating a focused beam of electrons, means for deflecting said focused beam across said charge storage .member in a predetermined manner, conne'ction means for a source of signal data for modulating said beam during said deection to write an electrical charge pattern on said charge storage member, means located on Ithe other side of said charge storage member for generating a beam of electrons for flooding a major portion ofthe surface area of said charge storage member to translate the char-ge pattern stored thereon into a corresponding visual presentation von said fluorescent screen, means for generating time-spaced pulses of electrical energy at a predetermined pulse repetition rate, and means coupled between said pulse generating means and said charge storage member for applying said pulses to said member during predetermined time intervals in which said focused beam is undeected.

7. A signal storage system including, an electrical storage tube having a charge storage member, a fluorescent screen, spaced from one side of said charge storage member, means for generating a focused beam of electrons, means for deecting said focused beam across said charge storage member in a predetermined manner, connection means for a source of signal data for modulating said beam during said dellection to write an electrical charge pattern on said charge storage member, means located on the other side of said charge storage member for generating a beam of electrons for ooding a major portion of `the surface area of said charge 4storage member to translate the charge pattern stored thereon into a corresponding visual presentation on said liuorescent screen, means for generating time-spaced pulses of electrical energy at a predetermined -pulse repetition rate, and means coupled between said pulse generating means and said charge storage member for applying said pulses to said member in the time intervals between successive deectionsof said focused beam.

8. A signal storage system including, an electrical storage tube having a charge storage member, a fluorescent screen spaced from one side of said charge storage member, means for generating a focused beam ofelectrons,

means vfor deecting said focused beam across said charge storage member in a .predetermined manner, connection means fora source of signal data for modulating said beam 4during said deection to write an electrical charge pattern `on said charge storage member, means located on the other side of said charge storage member for generating a beamof electrons for ooding a major portion of the surface area of said charge storage member to translate the charge pattern stored thereon into a correspondin-g visual presentation on said fluorescent screen, means for generating time-spaced pulses of electrical energy at a predetermined pulse repetition rate, and means coupled between said pulse generating means and said charge storage member for applying said pulses to said member in the time intervals between the establishing of successive electrical charge patterns.

9. A signal storage system including, `an electrical storage tube having a charge storage member, a cuorescent screen spaced from one side of said charge storage member, means for generating a focused beam of electrons, means. for deflecting said focused beam across said `charge storage member in a predetermined manner, connection means for a source of signal data for modulating said beam during said deflection to write an electrical char-ge pattern on said charge storage member, means located on the other side of said charge storage member for generating a beam of electrons for flooding a major por tion of the surface area of said charge storage member to translate the charge pattern stored thereon into a corresponding visual presentation on said Iuorescent screen,

means for generating `timespaced pulses of electrical energy at a predetermined pulse repetition rate, and means coupling said -pulse generating means to lsaid storage tube to pulse said storage member with respect to said flood beam `generating means during predetermined time intervals in which said focused beam is undeected.

10. A` signal storage system including, an electrical storage tube having an electron permeable charge storage member, means spaced from one side of said charge storage member'for providing a stream of electrons for flooding a major portion of the surface of said member, a fluorescent. viewing screen spaced from the opposite side of said charge storage member, means for providing a sharply dened and focused beam of electrons, means for deflecting said sharply defined and focused electron beam across said storage member, connection means for a source of signals for modulating said beam during said deflection to write an electrical charge pattern on said member, the charge pattern written on said member modulating the flow of said stream of electrons so that electrons passing through said electron permeable member impinge on said viewing screen and produce a visual display corresponding to said charge pattern, and means coupled to said charge storage member for repetitively generating pulses at a predetermined pulse repetition rate for periodically pulsing said storage member.

References Cited in the le of this patent UNITED STATES PATENTS 2,276,359 Von Ardenne Mar. 17, 1942 2,513,743 Rajchman July 4, 1950 2,532,339 Schlesinger Dec. 5, 1950 2,548,789 Hergenrother Apr. 10, 1951 2,613,634 Mesner Sept. 30, 1952 2,706,246 Klemperer Apr. 12, 1955 2,718,609 Covely Sept. 20, 1955 2,741,719 Reed .W Apr. 10, 1956 2,743,378 `Covely Apr. 24, 1956 

